This invention relates to a two-stage process for the conversion of light olefins into high VI lubricating oils. In the first stage, light olefins are oligomerized to intermediate range products which are then further converted into heavy hydrocarbons in a second stage.
Conversion of lower olefins to gasoline and/or distillate products is disclosed in U.S. Pat. Nos. 3,960,978 and 4,021,502 (Givens, Plank and Rosinski) wherein gaseous olefins in the range of ethylene to pentene, either alone or in admixture with paraffins, are converted into an olefinic gasoline blending stock by contacting the olefins with a catalyst bed made up of a ZSM-5 type zeolite. In a related manner, U.S. Pat. Nos. 4,150,062, 4,211,640 and 4,227,992 (Garwood et al) disclose processes for converting olefins by oligomerization/polymerization to gasoline and distillate, or heavier components. In U.S. Pat. No. 4,456,779 Owen et al disclose operating conditions for the Mobil Olefin to Gasoline/Distillate (MOGD) process for selective conversion of C.sub.3.sup.+ olefins to mainly aliphatic hydrocarbons. It is recognized that crystal size of a ZSM-5 type zeolite can affect selectivity, as discussed in U.S. Pat. No. 4,324,940 (Dessau). Additionally, U.S. Pat. No. 4,021,502 discloses conversion of olefins over ZSM-12, and U.S. Pat. No. 3,827,968 discloses a two step aromatization process wherein in the first step an olefin is contacted over a ZSM-5 type zeolite.
Multi-stage processing has been found advantageous for a number of olefin upgrading processes, such as U.S. Pat. No. 4,414,423. U.S. Pat. No. 4,361,477 discloses a 2-step process wherein a catalytic dewaxer effluent containing lower olefins is stabilized by contacting such effluent with a ZSM-5 type catalyst. However, none of this prior art is directed toward the concept of the use of a dual or two-stage process wherein light olefins are converted over ZSM-5 type catalyst to gasoline and/or distillate range liquids which are then converted under milder conditions and to lubricant quality products.